The present invention relates to a semiconductor laser module for mounting an optical semiconductor device into an inside thereof, and it also relates to an optical transmitter with using the semiconductor laser module therein.
An optical transmitter is used for transmitting a light with using a semiconductor laser therein, wherein a semiconductor module mounting a semiconductor laser is mounted on a substrate for use of heat radiation. For developing such the optical transmitter, it is necessary to obtain incidence and coupling of a light emitted from the semiconductor laser element with high efficiency (i.e., without causing a shift with respect to an optical axis). Relating to this, there are already known the following patent document:
Japanese Patent Laying-Open No. Hei 11-74395 (1999) <JP-A 11-74395> mentioned below discloses the module, comprising a frame made of metal, insulating material, or a complex of metal and insulating material, and a first bottom plate fixed on the frame and a second bottom plate fixed on the first bottom plate.
Also, Japanese Patent Laying-Open No. Hei 11-163184 (1999) <JP-A 11-163184> discloses therein that the semiconductor laser module is restricted in thickness of a screw portion and the substrate thereof, so as to take countermeasure against mismatching in the position that is caused when screwing the semiconductor device. And also, Japanese Patent Laying-Open No. 2001-28407 (2001) <JP-A 2001-28407> discloses provision of screw portions, projecting into an outside at a center along a long side of the substrate, so as to prevent the positional alignment of a semiconductor element and an optical filer from being out of order through the screw fixing. Further, Japanese Patent Laying-Open No. 2001-60735 (2001) <JP-A 2001-60735> discloses the provision of screw portions on both short sides of the substrate, so as to prevent an optical fiber from shifting in the optical axis when being fixed by the screw, and also that an optical fiber fixing member is disposed on one of the long sides of a frame while a reed terminal member on the other side thereof, for the purpose of preventing the optical fiber from shifting in the optical axis thereof when being fixed by the screw, etc. Furthermore, Japanese Patent Laying-Open No. Hei 11-74619 (1999) <JP-A 11-74619> discloses bonding of screw member made of a material, such as, metal, being equal or less than 200 GPa in the Young's modulus and equal or less than 500 MPa in yield stress, on a metal substrate and a metal frame constructing a package for use of an optical semiconductor, while projecting from the metal substrate and the metal frame.
In Japanese Patent Laying-Open No. 2002-72024 (2002) <JP-A 2002-72024>, shifting of the optical axis caused when fixing by the screw is dissolved, by flattening the bottom surfaces of a frame and a flange portion through gliding process.
[Patent Document 1]
Japanese Patent Laying-Open No. Hei 11-74395 (FIG. 1 and the explanation thereof)
[Patent Document 2]
Japanese Patent Laying-Open No. Hei 11-163184 (FIG. 1 and the explanation thereof)
[Patent Document 3]
Japanese Patent Laying-Open No. 2001-28407 (FIG. 1 and the explanation thereof)
[Patent Document 4]
Japanese Patent Laying-Open No. 2001-60735 (FIG. 1 and the explanation thereof)
[Patent Document 5]
Japanese Patent Laying-Open No. Hei 11-74619 (FIG. 1 and the explanation thereof), and
[Patent Document 6]
Japanese Patent Laying-Open No. 2002-72024 (FIG. 1 and the explanation thereof)
However, when mounting a semiconductor laser module on a heat radiation substrate, for building up a semiconductor laser transceiver, for example, and in particular, when driving the laser, the laser element generates heat, thereby generating thermal stress due to difference in the coefficient of linear expansion between the semiconductor laser module and the substrate for use of heat radiation thereof, and the thermal stress is also generated due to the change of temperature in the environments therearound. As a result of study made by the inventors earnestly, it causes to appear that it is difficult to dissolve the drawbacks, sufficiently, in accordance with the technologies disclosed in the documents mentioned above, such the shifting in the optical axis that is caused due to the thermal stress, which is generated with driving of the laser module.